In a Wideband Code Division Multiple Access (WCDMA) system, a Fractional Dedicated Physical Channel (F-DPCH) is used as one of downlink Dedicated Physical Control Channels (DPCCHs), and is configured to bear a Transmit Power Control (TPC) command generated in a physical layer. In a downlink, a configured TPC domain of the F-DPCH is used to estimate signal quality, that is, count a Bit Error Rate (BER) based on TPC symbols, for in-sync/out-of-sync decision and outer-loop power control, and channel quality detection.
In the prior art, the probability of occurrence of an event “polarities of in-phase/quadrature (I/Q) components of the TPC symbol are opposite to each other” in a counting period is p1, which is obtained through statistics, and the probability of occurrence of an event “a wrong decision is made on the TPC symbol and the polarities of the I/Q components of the TPC symbol are the same” is p2, which is obtained through statistics. The BER of the TPC symbol may be estimated according to the probabilities p1 and p2 obtained through statistics and the following formula (1):
                    BER        =                                            1              2                        ⁢                          p              1                                +                                    1              4                        ⁢                          (                                                p                  1                  2                                                  1                  -                                      p                    1                                                              )                                                          (        1        )            
During the implementation of the present invention, the inventors find that the prior art at least has the following defects. In the case that a channel condition is poor, that is, the TPC symbol has no path, the TPC symbols output by a RAKE receiver are all 0, p1 is 0 in this case, and then the BER obtained through the foregoing formula (1) is also 0, and such an estimation result is apparently inconsistent with an actual condition. It can be seen that, the solution in the prior art is not applicable to the case of an invalid TPC symbol, particularly, to the case where the TPC symbol has no path. At this time, the BER cannot be correctly estimated, thereby affecting the in-sync/out-of-sync decision and the outer-loop power control performance, and failing to correctly detect the channel quality.